That is true. given a graph x = siny you get the sine curve going up the y-axis.|dw:1347168918572:dw| ignore faults in sketch. But by the vertical line test this graph would not be a proper function. so we have to put boundaries. That graph can only by a proper function when x = -1 up to x = 1.

The function does not repeat, so no period. no amplitude in the traditional sense. amplitude refers to the regular sine functions that do repeat.
If you are referring to the distance in x from the function to the y-axis, same amplitude as y=sinx.

concept of using y = x is to draw a mirror or reciprocal of a given graph.
One reason for doing so with trig functions is to find some degree given a length.
Usually the question goes what is y= sinx where x is a given degree and y is the desired length.
Now the question would be "for what length y does degree x give for function sine?
so instead of just saying switch y with x, ask the question:
if y = sin(x) then y = sin (?) when y is given.
The graphing is to portray all possible values of (?) when y is given. then y becomes our independent variable while (?) becomes our dependent variable. drawing the results becomes a mirrored graph of sin(x) when reflected off the line y = x. as so:|dw:1347173789922:dw|